Method of making leaded-tin bronze alloys

ABSTRACT

A METHOD FOR MAKING A LEADED-TIN BRONZE ALLOY OF A PREDETERMINED COMPOSITION COMPRISES HEATING METAL SCRAP TO MAKE A LIQUID ALLOY THEREOF, MEASURING AND RECORDING THE TEMPERATURE OF A SAMPLE OF THE ALLOY WHILE THE SAMPLE COOLS TO A SOLID, WHEREBY THE THERMAL LIQUIDUS AND MONOTECTIC ARREST TEMPERATURES OF THE ALLOY ARE DETERMINED, AND ADDING SUFFICIENT QUANTITIES OF COPPER, TIN OR LEAD TO THE MOLTEN ALLOY TO OBTAIN A DESIRED THERMAL LIQUIDUS AND MONOTECTIC ARREST TEMPERATURES AND ACCORDINGLY THE DESIRED PREDETERMINED COMPOSITION OF THE ALLOY. THIS METHOD IS USEFUL IN CONTROLLING THE COMPOSITION OF LEADED-TIN BRONZE ALLOYS WITHOUT USING CONVENTIONAL ANALYTICAL TECHNIQUES.   D R A W I N G

1973' c. H. LATROBE 3,730,705

METHOD OF MAKING LvEADED-TTN BRONZE ALLOYS Filed March 1, i971 ALLOY2 ALLOYI ALLOY3\ a o ALLOY4 5 F I70F |76OF 0 92,2. lasso 18%|? V /ocu o 8 I6 24 32 B 40 %Pb LIQUIDUS TEMPERATURE PROFILE 4o %Sn H6 2 ALLOY2 ALLOY! ALLOYS ALl OY4 /ocu o s I6 24 32 a 40 /Pb loFb MONOTECTIC TEMPERATURE PROFILE INVENTOR.

CHARLES H. LATROBE BY Agent United States Patent 3,730,705 METHOD OF MAKING LEADED-TIN BRONZE ALLOYS Charles H. Latrobe, Baltimore, Md., assignor to Koppers Company, Inc., Pittsburgh, Pa. Filed Mar. 1, 1971, Ser. No. 119,599 Int. Cl. C22c 9/02 US. Cl. 7S-156 Claims ABSTRACT OF THE DISCLOSURE A method for making a leaded-tin bronze alloy of a predetermined composition comprises heating metal scrap to make a liquid alloy thereof, measuring and recording the temperature of a sample of the alloy while the sample cools to a solid, whereby the thermal liquidus and monotectic arrest temperatures of the alloy are determined, and adding sufficient quantities of copper, tin or lead to the molten alloy to obtain a desired thermal liquidus and monotectic arrest temperatures and accordingly the desired predetermined composition of the alloy.

This method is useful in controlling the composition of leaded-tin bronze alloys without using conventional analytical techniques.

BACKGROUND OF THE INVENTION This invention relates to a method for making leadedtin bronze alloys of a predetermined chemical composition and more particularly to a rapid method for determining the additional quantities of elemental copper, elemental tin and elemental lead that need to be added to a molten bath of such alloys in a furnace so that the alloy has the desired predetermined chemical composition.

Herein leaded-tin bronze alloys me'ans alloys consisting essentially of elemental copper, tin and lead. Leadedtin bronze alloys are used to make various machine parts such as, for example, gears, couplings, valves, piston sealing rings and the like, because such alloys have unique physical properties which render them useful for such applications. Machine parts made from leaded-tin bronze alloys are made by melting metal scrap containing elemental copper, tin and lead in a high frequency induction furnace to make a molten alloy thereof and casting the molten alloy into appropriately shaped molds. The chemical composition of the alloy must be adjusted to a predetermined composition while the molten alloy is in the furnace as the unique physical properties of the casting depend in great measure upon the chemical composition of the alloy.

Heretofore, the chemical composition of molten bronze alloys has been analyzed in a conventional manner by using elaborate and expensive analytical techniques such as, for example, wet chemical analysis, spectrographic analysis, X-ray diffraction analysis and the like. Although these conventional techniques are accurate and reliable, they require expensive equipment and skilled personnel are needed to operate such equipment. In some cases too much time is taken to determine the chemical composition of the alloys by the conventional techniques and often the molten alloy has been tapped from the furnace and poured into molds before the composition of the alloy is known.

DESCRIPTION OF THE PRIOR ART It is well known that an alloy of a specified chemical composition characteristically undergoes phase transformations at certain temperatures when the alloy is cooled from a liquid to a solid. To determine the temperature at which a phase transformation occurs a molten sample of the alloy is uniformly cooled from a liquid to a solid at a constant cooling rate and a cooling curve of temperature versus time that is a characteristic of the particular chemical composition of the alloy sample is developed. The temperatures of transformation appear as thermal arrests or as changes in the slope of the cooling curve.

Some alloy systems, for example, cast irons have at least two temperatures of transformation referred to as thermal arrest temperatures because the slope of the cooling curve momentarily changes and because the rate at which the alloy cools momentarily ceases when the alloy sample transforms from one phase to another phase. The first thermal arrest tem-perataure that is formed in cooling a specific alloy sample is the liquidus arrest temperature representing the temperature at which the alloy begins to solidify upon cooling. The second thermal arrest temperature is the solidus arrest temperature and represents the temperature at which the alloy completes its solidification upon cooling. More complex alloy systems, however, have a third and sometimes a fourth intermediate thermal arrest temperature, referred to as the monotectic arrest temperature, which temperature represents the temperature at which a single phase liquid alloy transforms into two phases; a solid phase and liquid phase of a second composition that is different from the composition of the initial liquid phase.

The liquidus arrest temperatures have heretofore been used to determine the carbon equivalences of cast irons. A sample is withdrawn from a molten bath of the cast iron, the sample is cooled, and a cooling curve of the sample is developed as the sample cools. For this purpose there is used a eutectometer, which comprises a refractory cup having a built-in thermocouple for disposal into the molten sample and a conventional recorder connected to the thermocouple for recording the cooling curve of the sample as it solidifies. A eutectometer is sold under the trademark Tectip. The liquidus temperature is observed from the cooling curve as an arrest or a change in the slope of the cooling curve and the carbon equivalence of the cast iron is thereby determined from standard tables that correlate the liquidus arest temperature with the carbon equivalence of the cast iron.

Liquidus arrest temperatures have also been used to determine the composition of simple copper alloys such as, for example, aluminum bronze (aluminum copper and tin) and single phase brass alloys (copper and zinc) as reported in D.- Arnauds article in Modern Casting, March 1970, entitled Thermal Analysis of Copper Alloys. The article states, the application of thermal analysis to ordinary bronzes is difficult and the obtained precision very questionable. As is well known the accuracy of determining the composition of an alloy by measuring the characteristic thermal arrest temperatures depends upon the extent to which a change in the amount of an individual element in the alloy changes the thermal arrest temperature. To illustrate this, for example, an increase of 0.08% carbon in cast iron reduces the liquidus temperature by about 20 F.; in a copper-tin binary alloy, however, an increase of 1% tin reduces the liquidus temperature by about 20 R; and in a copper-lead binary alloy, an increase of about 3% lead reduces the liquidus temperature by about 20 F. Consequently, the accuracy of the thermal analysis (particularly the use of liquidus arrest temperatures) of a copper-lead alloy or a copper-tin alloy as compared with the accuracy of the thermal analysis of a cast iron is such that the thermal analysis of the composition of copper lead-tin alloys or leaded-tin bronze alloys is not feasible. Chemical analysis is therefore used to precisely determine the composition of leaded-tin bronze alloys.

As is well-known the efiective solidus arrest temperature occurs at about 1410-1415" F. in leaded-tin bronze alloys although pure lead solidifies at about 606 F. and it does not change to any appreciable extent over a range of compositions as the effective solidus temperature indi- DETAILED DESCRIPTION cates the start of the peritectic transformation in tin-rich bronze alloys. Thus the measurement of the solidus arrest (A) Practlce mventlon temperature to determine the composition of leaded-tin In the p e f the lhYehtlehfhe ph f alley b ll i not f ibl as too h i i to be made in accordance wlth the lnventlon is selected, sumed in cooling the alloy to below the solidus arrest which alloy a a known standard chemical compositiontemperature of the alloy. The measurement of the mono- Herein foul" dlttefeht y designated as alleys tectic arrest temperature to determine the composition are used to illustrate the Practice Of e invention; of leaded-[in bronze alloys has not been heretofore 5 g. ever, it be recognized that these illustrations are not gested because very little information is known of the ihtehdeq to limit the Scope the ihVeIltlOIl- The e temperature isotherms on the monotectic surface of the Speclficatlohs of the foul Illustrative alloys are given copper-lead-tin ternary phase diagram. in the Table A helOWi Quite surprisingly, I have observed that in the case of leaded-tin bronze alloys each of the elements of copper, TABLE A tin and lead have a different effect upon the liquidus and Copp r, Tin, Lead, Nickel. upon the monotectic arrest temperatures of a leaded-tin Percent Peleent Percent Percent bronze alloy. I have discovered that in the method for Alloy No.1 7s s2 12-14. 4-6 0.75-1.25 making leaded-tin bronze alloys of a predetermined com- 238 15:17

3 0- 911 position the additional amount of 1nd1v1dual elements of Alloy No. 4 5-7 copper, tin, lead or combinations thereof that need to be added to a molten alloy to enable the production of an alloy of a predetermined chemical composition can be determined by measuring both the liquidus and monotectic arrest temperature. Conventional analytical tech- Metal scrap consisting essentially of the elements of copper, tin and lead, and preferably metal scrap having a chemical composition that is similar to the chemical specification of the preselected alloy, is charged into a niques need not be used for production control.

conventional high frequency 1nduct1on furnace having a SUMMARY THE I*IWENTION capacity of about 35 to 1,200 lbs. and is melted to make A method f Ina-king a ad d ti bronze alloy f a an alloy thereof. Other types of metal-making furnaces predetermined composition comprises heating a mixture be e acmn'iahee With the Invention although consisting essentially f the elements copper, tin and lead the 1nduct1on furnace is preferred for making leaded-tin to a liquid to make a liquid alloy thereof, measuring and brohze y recording the temperature of a sample of the alloy while After the metal SPrap has been melted to a molten the sample cools whereby the thermal liquidus and monoalloy, @Sarhple 1S wlthdravlfh from e molten bath In a tectic arrest temperatures of the alloy are determined, and cohvehhohal manner and 1S P Into e refractory adding sufficient quantities of the elements of copper, tin cup of the euteetometer whe eupon the cooling curve of or lead to the liquid alloy to obtain a desired thermal the sample 13 dPVeIOPCd 1h 3 cohvehhohal mahher- T liquidus and monotectic arrest temperatures and accordmolten Sample m refractorY P commences coohhg ingly h desired predetermined composition at a constant and uniform coollng rate of about 100 F.

per minute. The characteristic liquidus and monotectic GENERAL DESCRIPTION OF THE DRAWINGS 40 arrest temperatures are observed from the cooling curve.

In the drawings: The liquidus and monotectic arrest temperatures are FIG. 1 is a partial ternary phase diagram f copper, compared to one of the four tables Tables I-IV below tin and lead illustrating the temperature isotherms for (which correspond to the alloy to be made as indicated) the liquidus surface and; to determine if the alloy needs additional amounts of FIG. 2 is a partial ternary phase diagram of copper, elemental copper, tin or lead to have a final chemical tin and lead illustrating the temperature isotherms for composition within the limits of the standard chemical the monotectic surface. specification for the particular alloy.

TABLE I [For Alloy No. 1]

Monotectic arrest temperatures Liquidus arrest temperatures Sn Pb Cu Sn Pb Cu Sn Pb Cu Sn Pb Cu Sn Pb Cu Sn Pb Cu TABLE II [For Alloy No. 2]

Monotectic arrest temperatures Liquidus arrest temperatures Sn Pb 011 Sn Pb Cu Sn Pb Cu Sn Pb Cu Sn Pb 011 Sn Pb Cu 1, 652-1, 648--.- 2. 5 OK to pour OK to pour 1, 647-1, 642-.-. 3.0 OK to pour TABLE III [For Alloy N o. 3]

Monotectic arrest temperatures Llquidusisarresttemperatures Sn Pb Cu Sn Pb Cu Sn Pb Cu S11 Pb Cu Sn Pb Cu Sn Ib Cu TABLE IV [For Alloy N 0. 4]

Monotectic arrest temperatures Liquidus arrest temperatures Sn Pb Cu Sn Pb Cu Sn Pb Cu Sn Pb Cu Sn Pb Cu Sn Pb Cu 1,775-1,773 0.625 0.25 1,7721,770 0.5 5 0.75 1,760-1,767 0.5625 1.0 0.625 0 1.5 1, 61,764 0.5625 2.0 0. 0. 0 2.5 1,763-1,761 0.5625 3.0 0. .0 0.125 0.1875 0 3.5 1,760-1,75s 0.5625 3.0 0.31 .0 OKto pour .0 4.5 1,757-1,755 0.5625 5.0 0.3125 3.0 OKto pour .0 5.5 1,754-1,752 0.5625 6.0 0. 3125 4.0 OKto pour .0 6.5 1,751-1,740 0.5625 7.0 0.3125 -5.0 0062 .0 7.5 1,748-1,746 0.5625 3.0 0.3125 6.0 00625 .0 2.5

The values recorded in Tables I-IV are in terms of liquidus and monotectic arrest temperatures were 1728 F. weight percent of the total weight of the molten alloy and 1520 F. respectively. According to Table I, the of additional elements that need to be added. Table I is observed liquidus and monotectic arrest temperatures were used to make an alloy having a chemistry within the limwithin the OK to Pour region of Table I, indicating its of Alloy No. 1 above; Table II is used to make Alloy the alloy had a chemical composition within the specifi- No. 2; Table III is used to make Alloy No. 3; and, Table 3 cations for Alloy No. 1. The molten alloy was then super- IV is used to make Alloy No. 4. heated to a temperature of about 2200 F.; the alloy was The percentage of additional elemental copper, tin or tapped from the furnace and poured into the appropriate lead is read from the proper table and the actual weight molds in the conventional manner.

amount of additional elements needed is determined by multiplying the percentage of each element to be added to (B) Determination of Tables LIV the alloy by the total weight of the molten alloy in the Tables I-IV for the standard alloys of this invention fur ti e 100, were developed by trial and error techniques. Initially The additional elements are added to the molten alloy P s of each Standard table Were developed y melting and thoroughly melted and mixed therein. After the adan per mental 30 pound heat of copper, tin and lead ditions are melted, the thermal arrest temperatures are in an induc ion furnace and determining the liquidus and again observed in accordance with the invention to be monotectic arrest temperatures and the actual chemical sure that the thermal arrest temperatures are within the 0mp0siti0n of he alloy by wet chemistry techniques of desired ranges and accordingly the desired chemical comthis molten alloy. While the alloy was molten a selected position of the alloy has been obtained. The temperature amount of lead was added to the molten alloy and melted of the molten alloy is brought to the desired final tapping thcrein Without adding y amounts of pp r of tin i temperature; the molten alloy is tapped from the furnace the molten alloy. Subsequently, the liquidus and monoand is poured into appropriate molds. tectic arrest temperatures and the actual chemical compo- As an example of my invention, an alloy having the sition were again determined. This procedure was rechemical specification of Alloy No. 1 above was selected. peated for a series of incremental changes in the amount About 1,000 lbs. of bronze ingot and scrap containing of lead in the molten alloy. The same procedure was copper, tin and lead were charged into a 1,200 lb. high used for a series of incremental changes in the amount of frequency induction furnace and melted to a molten alloy tin in the molten alloy without adding any amounts of in about forty-five minutes. Subsequently a two pound copper or lead in the molten alloy. sample of the molten alloy was withdrawn from the From these initial tests the amounts needed to bring furnace with a sample cup and was poured immediately 0 the alloy into specification were determined and correinto the refractory cup of the eutectometer. The molten lated to the respective liquidus and monotectic arrest temsample in the refractory cup commenced cooling at about peratures. Subsequently, complete standard tables for each 100" F. per minute. The recorder of the eutectometer proalloy were prepared by using the additions initially deterduced a complete cooling curve of the sample in about mined and by extrapolating new additions for different five minutes. The liquidus and monotectic arrest temperaliquidus and monotectic arrest temperatures not detertures were read and found to be 1738 F. and 1522 F. mined by wet chemistry techniques. Over a period of time respectively. Reading Table I for Alloy No. 1, the alloy the additions in the standard tables were modified on a needed /2 by weight of tin and A by weight of lead trial and error basis until the tables as now shown herein to have a composition conforming to the chemical speciwere developed having an accuracy sufiicient for comfication of Alloy No. 1. Thus, five pounds of elemental mercial usage in accordance with the invention. tin and two and one-half pounds of elemental lead were Tables I-IV do not provide the chemical composition added to the molten bath, thoroughly melted and mixed of the alloy but merely show the percentage amount of therein in about two minutes. As a check, a two pound additional elements needed to bring the alloy into its second sample was withdrawn from the furnace and chemical specification. Each table indicates an OK. to

poured into the refractory cup of the eutectometer. The pour region indicating the liquidus and monotectic arrest temperatures for the alloy when the alloy has its proper chemical specification. The actual chemical compositions of the alloy, however, are known in the OK. to pour region as indicated in Table B below:

percent Sn=the percent of tin added to the molten alloy percent Pb=the percent of lead added to the molten alloy percent Cu=the percent of copper added to the molten alloy Each element of copper, tin and lead have varying effects on both the liquidus and monotectic arrest temperatures as expressed by the following simultaneous equations for each of the standard alloys:

ALLOY N0. 1

'Equation No. 1

1727 F.T =I8 (percent Sn)8 (percent Pb) 1519 F.-T =12 (percent Sn)+14 (percent Pb) Equation No. 2

1727 F.T =--8 (percent Pb)+ (percent Cu) 1519 F.=T ++14 (percent Pb)+ /2 (percent Cu) Equation No. 3

1727 F.T =-18 (percent Sn)l-S (percent Cu) 1519 F.T =12 (percent Sn)+ /2 (percent Cu) ALLOY NO. 2

Equation No. 1

1647 F.T =--24 (percent Sn)8 (percent Pb) 1483 F.T =-12 (percent Sn)+24 (percent Pb) Equation No. 2 1647" F.T ='8 (percent Pb)+6 (percent Cu) 1483 F.T =+24 (percent Pb)' /2 (percent Cu) Equation No. 3 l647 F.-T =24 (percent Sn)+6 (percent Cu) 1483 F.T =l2 (percent Sn)Vz (percent Cu) ALLOY NO. 3

Equation No. 1 1720 F.T =18 (percent Sn)12 (percent Pb) 1598 F.-T =8 (percent Sn)+8 (percent Pb) Equation No. 2 1720 =F.-T ='12 (percent Pb)+4 (percent Cu) 1598 F.T -=+8 (percent Pb)+- /2 (percent Cu) Equation No. 3

1720 F.-T =-18 (percent Sn)l-|-4 (percent Cu) 1598 F.T ;=-8 (percent Sn)+- /2 (percent Cu) ALLOY NO. 4

Equation No. 1

1758 F.-T =22 (percent Sn)7 (percent Pb) 1666 F.T ;=12 (percent Sn)l-4 (percent Pb) Equation No. 2

1758" F.T =7 (percent Pb)+3 (percent Cu) 1666 F.T =+4 (percent Pb)+0 (percent Cu) Equation No. 3

1758 F. T ;=-22 (percent Sn)+3 (percent Cu) 1666 F.T =12 (percent Sn)+0 (percent Cu) where T =the observed liquidus arrest temperature T =the observed monotectic arrest temperature These equations mathematically illustrate the percentage amount of copper, tin, or lead that may be added to the molten alloy to change the liquidus or monotectic arrest temperatures. Tables I-IV were based on the equations; however, if the measured liquidus or monotectic temperatures are beyond the limits of the chart, then the equations must be used to determine the percentage amounts of copper, tin, or lead that must be added to the molten alloy to bring the liquidus and monotectic temperatures within the OK. to pour region.

For example, in the case of Alloy No. 1, a 1% addition of tin to the molten alloy will reduce the liquidus arrest temperature by 18 F. and reduce the monotectic arrest temperature by 12 F.; a 1% addition of lead will reduce the liquidus arrest temperature by 14 F and a 1% addition of copper will increase the liquidus arrest temperature by 5 F. but will reduce the monotectic arrest temperature by /2 F.

The constant temperature values in each equation represent the thermal arrest temperatures when the alloy is within its proper chemical specification for each standard alloy. In the case of Alloy No. 1, when the observed liquidus temperature (T 1727 F. and the observed monotectic arrest temperature (T is 1519 F. the alloy should have 12.75% $0.25 tin, 4.75 $0.25 lead and a balance of copper. Hence, by solving the simultaneous equations, the amount of additions to the molten alloy may be determined so that the alloy has a composition within the limits of its specification. For example, in the case of Alloy No. 1 if the observed liquidus arrest temperature were 1770 F. and the observed monotectic arrest temperature were 1529 F. about 2% tin and 1% lead should be added to the molten alloy to bring its chemical composition into specification.

The temperature isotherms for the liquidus surface in the partial ternary phase diagram of copper, tin, and lead are illustrated in FIG. 1. These isotherms are approximations developed by superimposing the data from Table B above on a diagram taken from a reference work entitled Chill Cast Tin Bronzes by D. Hanson and W. T. Pell- Walpole, published by Edward Arnold and Company, London, England, in 1951, particularly pages 74-76. The isotherms show that, as the amount of lead or tin increases, the liquidus arrest temperature decreases; however, tin decreases the liquidus arrest temperature more so than lead.

The temperature isotherms shown on both FIGS. 1 and 2 are taken from the above-noted reference; however, the parallelograms for Alloys 1-4 are located according to their approximate chemical compositions. When thus located, the liquidus and monotectic temperatures for each are as indicated in Table -B; the temperatures for these alloy compositions differ somewhat from the reference temperatures most likely because they were not measured according to the method used in the reference; instead, they were measured by a conventional cooling curve technique. The reference temperatures are used as guidelines for comparison.

The temperature isotherms for the monotectic surface in the partial ternary phase diagram of copper, tin and lead are illustrated in FIG. 2. The monotectic temperatures obtained by the inventor, as illustrated in FIG. 2, differ from those in the reference work because the former were not measured under equilibrium conditions. The isotherms show that, as the amount of tin increases, the monotectic arrest temperature decreases; but, as lead is added the monotectic arrest temperature increases.

It should be noted that the liquidus and monotectic arrest temperatures are combined on a single diagram in the reference work but are shown individually in FIGS. 1 and 2 respectively for clarity. Both FIGS. 1 and 2 illustrate the chemical compositions of the four particular alloys discussed herein. The larger parallelograms delineate the broad chemical specifications of the alloys as recited in Table A and the smaller parallelograms delineate the known chemical composition of the alloys as recited in Table B. Line AB in both FIGS. 1 and 2 shows the limit of miscibility in leaded-tin bronze alloys.

By examining both FIGS. 1 and 2 it can be seen why both the liquidus and monotectic arrest temperatures must be used to determine the amount of elemental copper, tin or lead that must be added to the alloy so that the alloy has its proper predetermined composition. The liquidus temperature isotherms in FIG. 1 extend generally across the copper-rich corner, from the tin side to the lead side of the diagram whereas the monotectic temperature isotherms of FIG. 2 extend generally from the copper-rich corner. The liquidus and monotectic temperature isotherms criss-cross each other. Hence, when both the liquidus and monotectic arrest temperatures are known the composition of the alloy is specifically known within a range of accuracy suflicient for product control. If, for example, the liquidus temperature were 1725 F. and the monotectic temperature were unknown the alloy could have a chemical composition conforming to either Alloy Nos. 1 or 3. But if, in the same case, monotectic temperature were 1520 F. then the alloy would have a chemical composition conforming to Alloy No. 1 or if the monotectic temperature were 1598 F. then the alloy would have a chemical composition conforming to Alloy No. 3. As previously pointed out, these temperatures were measured by a conventional cooling curve technique and appear on Table B and are not the same as the reference temperatures.

While the invention has ben described and disclosed with particularity in reference to the four standard alloys herein it will be recognized that the invention may be practiced for other bronze alloys than the four disclosed herein. Merely by trial and error techniques standard tables can be developed for other such alloys consisting essentially of copper, tin and lead and used for determining the amount of additional elements that need to be added to such molten alloys to bring their chemical composition into specification.

In the claims:

1. A method for making a leaded-tin bronze alloy of a predetermined composition comprising:

(a) heating a mixture consisting essentially of the ele ments of copper, tin, and lead to a liquid to make a liquid alloy thereof,

bronze alloy has the following composition:

Percent Copper 78-82 Tin 12-14 Lead 4-6 Nickel 0.75-1.25

has a thermal liquidus arrest temperature of 1720-1734 F. and has a thermal monotectic arrest temperature of 1515-1524 F.

3. The method of claim 1 wherein said leaded-tin bronze alloy has the following composition:

Percent Copper 78-82 Tin 15-17 Lead 4-6 has a thermal liquidus arrest temperature of 1642-1652 F. and has a thermal monotectic arrest temperature of 1479-148 6 F.

4. The method of claim 1 wherein said leaded-tin bronze alloy has the following composition:

Percent Copper 78-82 Tin 9-11 Lead 8-11 has a thermal liquidus arrest temperature of 1716-1725 F. and has a thermal monotectic arrest temperature of 15951600 F.

5. The method of claim 1 wherein said leaded-tin bronze alloy has the following composition:

Percent Copper 76.5-79.5 Tin 5-7 Lead 14-18 has a thermal liquidus arrest temperature of 1752-1760 F. and has a thermal monotectic arrest temperature of 1663-1668 F.

References Cited UNITED STATES PATENTS Re. 12,880 11/1908 Clamer et a1. -156 655,402 8/ 1900 Hendrickson et a1. 75-156 X 1,584,706 5/1926 Day 75-156.5 X 1,686,277 10/1928 Judy 75-156 1,790,164 1/1931 Merten 75-156 CHARLES N. LOVELL, Primary Examiner J. E. LEGRU, Assistant Examiner U.S. Cl. X.R. 75-135 

